Spatial distribution of physical and chemical variables and macroinvertebrate composition, structure and functional aspects were investigated in five microhabitats available (Ranunculus acquatilis+ Ranunculus sardous, Spirogyra sp., Juncus effusus, and unvegetated littoral sediments and central sediments) in a temporary pond near Rome during spring 2004. The central sediments were found to differ greatly from the other substrates. They were characterized by higher nutrient contents (total P, total N), organic matter and organic C, and silt and clay in the sediments, and lower dissolved oxygen content and lower pH in the water. Species richness and densities of total macrofauna showed the lowest values in central sediments and the highest ones in submerged macrophytes (Ranunculus spp.) and emergent vegetation (Juncus effusus). Oligochaeta Tubificidae, some Nematoda (Dorylaimus spp.), and Chironomidae Tanypodinae (Procladius sp. and Psectrotanypus varius) and Chironominae (Chironomus plumosus group) characterized the central sediments, whereas Ephemeroptera and most of the Odonata and Coleoptera species were commonly found in submerged macrophyte beds. Some species of Coleoptera and Hemiptera (Hygrobia hermanni, Helochares lividus, Berosus signaticollis and Gerris maculatus) were mainly found in the algal substratum, and some Nematoda species (Tobrilus spp. and Aporcelaimellus obtusicaudatus), Oligochaeta Enchytraeidae, young larvae of Sympetrum and Diptera Ceratopogonidae in littoral sediments. Juncus effusus appeared to be mainly colonized by Chironomidae Orthocladiinae (Psectrocladius sordidellus group and Cotynoneura scutellata) and Tanytarsini (Paratanytarsus sp.). Central sediments also favoured high abundances of collector-gatherers, burrowers and drought resistant forms with passive dispersal, whereas Ranunculus spp. hosted mainly scrapers, shredders, swimmers+divers and active dispersal forms without any resistant stages to desiccation. Juncus plants were mostly colonized by collector-filterers and by organisms capable of both active dispersal and surviving desiccation. Littoral sediments and algae showed similar functional organization and intermediate features between central sediments and submerged macrophyte beds. All these results demonstrate that microhabitat characteristics play a crucial role in selecting macroinvertebrate taxa according to their environmental requirement, feeding mechanism, movement and resistance to drought. Moreover, our study confirms the role of submerged and emergent vegetation in maintaining high biodiversity and suggests that all microhabitats should be considered to provide both an exhaustive collection of species for pond management and conservation and basic insights into the functioning of pond communities. (C) 2009 Elsevier GmbH. All rights reserved

Twenty astatic ponds near Rome were studied in order to define the relationships between physicochemical variables and macroinvertebrate communities. The main abiotic factor differentiating the ponds was the annual hydrologic cycle. Depth, surface area, and sand percentages in the sediment were higher in permanent ponds, whereas silt+clay content was higher in temporary ones. No difference was recorded in pH, conductivity and oxygen content in the water or organic matter in the sediments between the two pond types. Three main ecological assemblages were distinguished: a) generalist taxa common to both pond types; b) taxa associated with and adapted to temporary ponds; and c) taxa which seemed to prefer permanent ponds. Overall, there was no relationship between number of taxa and surface area, except for Odonata and aquatic macrophytes. A positive correlation was observed between number of macrophyte species and macroinvertebrate taxa richness, and particularly of odonates and chironomids, suggesting that an increase in aquatic vegetation species leads to an increase in microhabitats and suitable food, substrate, andor refuge from predators. Odonata seemed also to prefer more stable and sunny ponds. DICOTYLEDONES Um belliferae Callitrichaceae Apium inundatum (L.) Reichenb. Fil CaNitriche obfusangula Le Gall Oenanfhe sp. Callifriche stagnalis Scop. Ceratophylhceae MONOCOTYLEDONES Ceratophyllum submersum L. Alismataceae Elatinncepe Alisma lanceolafum With. Elatine alsinastrum L. Damasonium alisma Miller Haloragaeepe Juncaceae Myriophyllum alternijlorum DC. Juncus efisus L. Labiatae Lemnaceae Mentha pulegium L. Lemna minor L. Lentibnlariaceae Poaceae Ufricularia vulgaris L. Agrostis sp. Polygonaceae Gliceria notafa Chevall. Polygonum sp. Phragmifes australis Cavill Ranunculaceae Potamogetonaceae Ranunculus aquatilis L. Pofamogefon natans L. Ranunculus ophioglossifolius Vill. Potamoge ton polygonifolius Poumt Ranunculus peltatus Schrank Potamogeton trichoides Cham. and Schlecht

-The macroinvertebrate fauna of twenty-one ponds (thirteen temporary and eight permanent) located in four protected areas in Central Italy were studied in March, May and June 2002, with the aim to bring out relationships between environmental variables and the functional characteristics (functional feeding groups, habits and resistance to drought) of communities. Macroinvertebrates were collected in three mesohabitat types (macrophyte beds, littoral sediments, central sediments). Overall, the functional attributes of temporary and permanent pond communities did not differ greatly. However, at the mesohabitat scale, collector-gatherers, burrowers and permanent residents capable of passive dispersal were more abundant in sediments. Scrapers and shredders, sprawlers and climbers, swimmers and divers, and organisms capable of active dispersal which lack drought resistance were more abundant in macrophyte beds. Although hydroperiod is the main driving factor affecting community structure, our results suggest that it remains an unimportant factor in controlling functional traits, which appeared to be more influenced by substratum types. Moreover, the positive relationship between taxonomic and functional diversity metrics indicates that an increase in taxonomic richness induces a satisfactory partitioning of the ecological resources among taxa, thus maintaining the ecological complexity of the ponds regardless of their hydroperiod length.

pubblicato per ora onlin

1. In Italy small water bodies, especially temporary ones, have been little studied. As a consequence, their conservation value as a biodiversity resource is often overlooked despite Mediterranean temporary waters being listed as a priority habitat in the Habitats Directive (92/43/EEC). 2. A monitoring programme was designed to determine which factors influence pond species richness, and to analyse the variation in macroinvertebrate community structure within and among ponds. Three main contrasting mesohabitats (macrophyte beds, littoral sediments and central sediments) were defined within 21 ponds (8 permanent and 13 temporary) along the Tyrrhenian coast of Italy near Rome, from which invertebrate macrofauna was collected in March, May and June 2002. 3. The main environmental factors influencing the number of species in ponds were hydroperiod length, depth, Surface area, dissolved oxygen concentration and macrophyte species richness. Temporary ponds contained a smaller number of taxa than permanent ponds, but both types of ponds supported similar numbers of rare and threatened species. The total number of species, and in particular Coleoptera, Odonata, and Hemiptera, was higher in macrophyte beds than in both littoral and central sediments. 4. Multivariate analysis (non-metric multidimensional scaling) showed that the overall variation in assemblage composition was greater between temporary and permanent ponds than all-long mesohabitats, suggesting that environmental variables, such as hydroperiod, have a stronger effect oil macroinvertebrate communities than substratum type. 5. In terms of species of conservation interest, this study suggests that both pond types and all mesohabitats should be considered in order to obtain a correct evaluation of pond conservation value. Copyright (c) 2005 John Wiley & Sons, Ltd